More verbosity (and other) fixes for v9

[Jutho]

Among other things, also only print the non-hermitian warning in the LanczosIterator if verbosity >= WARN_LEVEL.

Also deprecate mul! in favour of unproject!! to reflect the bangbang nature of this method.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.07%. Comparing base (15988e1) to head (8bfa694).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #116      +/-   ##
==========================================
+ Coverage   88.04%   88.07%   +0.02%     
==========================================
  Files          32       32              
  Lines        3397     3395       -2     
==========================================
- Hits         2991     2990       -1     
+ Misses        406      405       -1     

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